A propeller power generator that generates electrical power by rotating a propeller with wind, ocean current, and other fluids has been known. A wind power generator, for example, converts mechanical energy of a propeller that rotates by receiving wind into electrical energy by using a generator.
A propeller power generator may include a position sensor such as an encoder that detects the rotational position of a propeller of the generator. Some power generators of related art have such a position sensor onto a propeller shaft. The position sensor detects the rotational position of the propeller shaft, thereby detecting the rotational position of the propeller. (Refer to Japanese Patent Application Laid-open No. 2011-208635, for example.)
However, the propeller shaft generally has a large shaft diameter, which may cause the position sensor to become larger when installed on the propeller shaft.